Drug-impaired driving incidents in Canada increased 42% above projected trends after 2018 legalization, but the increase was more associated with enhanced police enforcement and pandemic effects than with cannabis sales.
Traffic safety researchers, drug policy analysts, law enforcement agencies, and anyone evaluating cannabis legalization outcomes
What the researchers found
Post-2018, police reported 65 extra drug-impaired incidents per million annually (42% above trend) and 280 extra alcohol-impaired incidents per million (17% above trend); increases were associated more with drug recognition expert employment and pandemic restrictions than cannabis sales.
Why it matters
The headline finding — more impaired driving after legalization — is misleading without context. Enhanced enforcement capacity (more drug recognition experts) detected more cases that previously went unrecorded.
The numbers in context
65 extra drug-impaired incidents/million/year (42% above trend); 280 extra alcohol-impaired incidents/million/year (17%); drug-impaired positively associated with drug expert employment (p<0.05) and cannabis sales (p<0.05).
How the study worked
Interrupted time-series analysis of province-level annual police-reported impaired driving counts (2009-2023), with regressions testing associations with legal cannabis sales, use prevalence, police drug experts, and COVID-19 restrictions.
What this study cannot tell us
Police-reported data reflects enforcement activity, not actual impairment prevalence; cannot distinguish cannabis from other drug impairment in most cases; province-level analysis may mask local variation.
How to read the evidence
Robust interrupted time-series analysis with multiple covariates, but police-reported data inherently reflects enforcement patterns, not just behavior.
When this study was published
Published in 2026 with data through 2023, providing 5 years of post-legalization trend data.
The bigger picture
This highlights a fundamental measurement challenge: when you improve detection, reported rates rise even if actual behavior doesn't change — a dynamic policymakers must understand when evaluating legalization outcomes.
Questions still open
- What proportion of the increase represents genuinely new impaired driving versus improved detection? How should impaired driving metrics be adjusted for enforcement capacity changes?
Common questions
Did cannabis legalization increase impaired driving in Canada?
Are more people actually driving high, or are police just catching more?
Read the original research
Police-Reported Impaired Driving After Recreational Cannabis Legalization in Canada.
American journal of preventive medicine, 70(2), 108176
Citation
Armstrong, Michael J. (2026). Police-Reported Impaired Driving After Recreational Cannabis Legalization in Canada.. American journal of preventive medicine, 70(2), 108176. https://doi.org/10.1016/j.amepre.2025.108176
Explore the wider topic
- Cannabis Law and Your Rights: A Complete 2026 Guide
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